U.S. patent number 7,540,892 [Application Number 11/471,582] was granted by the patent office on 2009-06-02 for hydrogen gas generation system.
This patent grant is currently assigned to Millennium Cell Inc.. Invention is credited to Richard M. Mohring, Michael Strizki.
United States Patent |
7,540,892 |
Strizki , et al. |
June 2, 2009 |
Hydrogen gas generation system
Abstract
A system for generating hydrogen gas utilizes a volume exchange
housing for the storage of a fuel material that reacts to generate
hydrogen gas and a hydrogen separation chamber. The system includes
a gas permeable membrane or membranes that allow hydrogen gas to
pass through the membrane while preventing aqueous solutions from
passing therethrough. The system is orientation independent. A
throttle valve is also used to self regulate the reaction
generating the hydrogen gas.
Inventors: |
Strizki; Michael (Hopewell,
NJ), Mohring; Richard M. (East Brunswick, NJ) |
Assignee: |
Millennium Cell Inc.
(Eatontown, NJ)
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Family
ID: |
32771331 |
Appl.
No.: |
11/471,582 |
Filed: |
June 21, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060236606 A1 |
Oct 26, 2006 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10359104 |
Feb 5, 2003 |
7105033 |
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Current U.S.
Class: |
48/61; 422/106;
48/67; 48/198.8; 48/127.9; 423/289; 422/242; 422/236; 422/198;
422/112; 429/515 |
Current CPC
Class: |
C01B
3/065 (20130101); C01B 3/501 (20130101); F17C
11/005 (20130101); H01M 8/04208 (20130101); H01M
8/0662 (20130101); H01M 8/065 (20130101); Y02E
60/32 (20130101); C01B 2203/0405 (20130101); H01M
8/04216 (20130101); Y02E 60/36 (20130101); Y02E
60/50 (20130101); C01B 2203/0495 (20130101); C01B
2203/0465 (20130101) |
Current International
Class: |
B01J
7/00 (20060101) |
Field of
Search: |
;422/198,306,236,242,211
;429/17,19 ;48/61 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 170 249 |
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Jan 2002 |
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EP |
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1 375 419 |
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Jan 2004 |
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EP |
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WO 01/51410 |
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Jul 2001 |
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WO |
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WO 03/004145 |
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Jan 2003 |
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WO |
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Other References
Maurice E. Indig and Richard N. Snyder, "Sodium Borohydride, an
Interesting Anodic Fuel." Journal of the Electrochemical Society,
vol. 109, pp. 1104-1106, Nov. 1962. cited by other.
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Primary Examiner: Neckel; Alexa D.
Assistant Examiner: Handal; Kaity V.
Attorney, Agent or Firm: Dickstein Shapiro LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser.
No. 10/359,104, filed on Feb. 5, 2003, now U.S. Pat. No. 7,105,033,
which is incorporated herein by reference in its entirety.
Claims
We claim:
1. A hydrogen generator comprising: a fuel storage chamber
configured to contain a fuel material capable of reacting to
generate hydrogen gas; a hydrogen separation chamber; and a
catalyst chamber configured to contain a catalyst capable of
promoting reaction of the fuel material to generate hydrogen gas
and discharged fuel; wherein the catalyst chamber is in fluid
communication with the fuel storage chamber and the hydrogen
separation chamber such that the fuel material can exit the fuel
storage chamber and enter the catalyst chamber, and the hydrogen
gas and discharged fuel can exit the catalyst chamber and enter the
hydrogen separation chamber; and wherein the fuel storage chamber
has a gas permeable membrane capable of allowing hydrogen gas to
pass from the chamber while preventing the fuel material from
passing therethrough.
2. The hydrogen generator of claim 1, wherein the hydrogen
separation chamber has a gas permeable membrane.
3. The hydrogen generator of claim 1, further comprising an outer
housing and wherein both of the fuel storage chamber and the
hydrogen separation chamber are within the housing.
4. The hydrogen generator of claim 3, further comprising a
partition within the housing and wherein the fuel storage chamber
and the hydrogen separation chamber are separated from each other
by the partition.
5. The hydrogen generator of claim 3, further comprising at least a
first hydrogen gas outlet, proximate the hydrogen separation
chamber, for discharging hydrogen gas from the housing.
6. The hydrogen generator of claim 5, further comprising a second
hydrogen gas outlet, proximate the fuel storage chamber.
7. The hydrogen generator of claim 4, wherein the partition is
flexible.
8. The hydrogen generator of claim 4 wherein the partition is
configured to allow hydrogen gas from the gas permeable membrane in
the fuel storage chamber to combine with hydrogen gas from the
hydrogen separation chamber in a space between at least one of the
fuel storage chamber or the hydrogen separation chamber and the
housing.
9. The hydrogen generator of claim 8, further comprising a hydrogen
gas outlet configured to pass the combined hydrogen gas out of the
housing.
10. The hydrogen generator of claim 1, wherein the fuel storage
chamber and the hydrogen separation chamber are located in a
housing and are separated from each other by a movable
partition.
11. The hydrogen generator of claim 1, wherein the fuel storage
chamber comprises a first flexible bag for containing the fuel
material and the hydrogen separation chamber comprises a second
flexible bag for containing the discharged fuel.
12. The hydrogen generator of claim 11, wherein the at least one
gas permeable membrane is located in a wall of at least one of the
flexible bags.
13. The hydrogen generator of claim 11, wherein the at least one
gas permeable membrane is located in a wall of at least one of the
flexible bags.
14. The hydrogen generator of claim 12, wherein each of the
flexible bags comprises a wall having a gas permeable membrane.
15. A hydrogen gas generator, comprising a housing containing a
fuel storage area and a hydrogen separation area, wherein each area
is bounded by at least one wall comprising a hydrogen permeable
membrane configured to permit hydrogen gas to pass through the
respective wall; at least a first hydrogen gas outlet configured to
pass hydrogen gas from the housing; a reaction chamber; a fuel
conduit capable of conveying fuel from the fuel storage area to the
reaction chamber; a discharged fuel conduit capable of conveying
discharged fuel and hydrogen gas from the reaction chamber to the
hydrogen separation area.
16. The hydrogen gas generator of claim 15, wherein the hydrogen
permeable membrane comprises a material selected from the group
consisting of silicon rubber, fluoropolymers, and hydrogen
permeable metals.
17. The hydrogen generator of claim 15, wherein at least one of the
hydrogen separation and fuel storage areas is bounded by a flexible
bag.
18. The hydrogen generator of claim 17, wherein each of the areas
is bounded by a flexible bag.
19. The hydrogen generator of claim 17, wherein the respective
areas are located side by side within the housing.
20. The hydrogen generator of claim 15, wherein the respective
areas are separated by a movable partition within the housing.
21. The hydrogen gas generator of claim 20, wherein the partition
is flexible.
22. The hydrogen gas generator of claim 20, wherein the partition
is configured such that hydrogen gas can pass from one side of the
partition within the housing to the other side of the
partition.
23. The hydrogen generator of claim 15, further comprising a space
between at least one of the areas and the housing, wherein the
space is capable of containing hydrogen gas from at least one of
the respective areas before the gas passes through the hydrogen gas
outlet.
24. The hydrogen generator of claim 15, further comprising a space
between at least one of the areas and the housing, wherein the
space is capable of containing hydrogen gas from both of the
respective areas before the gas passes through the hydrogen gas
outlet.
25. The hydrogen generator of claim 15, wherein the reaction
chamber comprises a supported catalyst capable of enhancing the
generation of hydrogen from fuel stored in the fuel storage
area.
26. A hydrogen gas generator comprising: a housing containing a
fuel storage area and a hydrogen separation area, wherein each area
is bounded by at least one wall comprising a hydrogen permeable
membrane configured to permit hydrogen gas to pass through the
respective wall and wherein each area is separated by a movable
partition within the housing, wherein the partition is configured
such that hydrogen gas can pass from one side of the partition
within the housing to the other side of the partition; at least a
first hydrogen gas outlet configured to pass hydrogen gas from the
housing; a reaction chamber; a fuel conduit capable of conveying
fuel from the fuel storage area to the reaction chamber; and a
discharged fuel conduit capable of conveying discharged fuel and
hydrogen gas from the reaction chamber to the hydrogen separation
area.
27. The hydrogen gas generator of claim 26, wherein the partition
comprises a gas permeable membrane.
28. The hydrogen gas generator of claim 27, wherein the hydrogen
permeable membrane comprises a material selected from the group
consisting of silicon rubber, fluoropolymers, and hydrogen
permeable metals.
29. The hydrogen gas generator of claim 26, wherein the partition
comprises a hydrogen gas permeable material.
30. A hydrogen gas generator comprising: a housing containing a
fuel storage area and a hydrogen separation area, wherein each area
is bounded by at least one wall comprising a hydrogen permeable
membrane configured to permit hydrogen gas to pass through the
respective wall; at least a first hydrogen gas outlet configured to
pass hydrogen gas from the housing; a reaction chamber; a fuel
conduit capable of conveying fuel from the fuel storage area to the
reaction chamber; a discharged fuel conduit capable of conveying
discharged fuel and hydrogen gas from the reaction chamber to the
hydrogen separation area; and further comprising a space between at
least one of the areas and the housing, wherein the space is
capable of containing hydrogen gas from both of the respective
areas before the gas passes through the hydrogen gas outlet.
31. The hydrogen generator of claim 30, wherein each of the areas
is bounded by a flexible bag.
32. The hydrogen generator of claim 30, wherein the respective
areas are located side by side within the housing.
33. The hydrogen generator of claim 30, wherein the respective
areas are separated by a movable partition within the housing.
34. The hydrogen gas generator of claim 30, further comprising a
second hydrogen gas outlet.
Description
FIELD OF THE INVENTION
The invention relates to a system for generating hydrogen gas using
a catalyst from a fuel such as borohydride. More particularly, the
invention relates to a system for hydrogen generation having a
volume-exchange system for the storage of fuel solution and
discharged product and a hydrogen filtration system.
BACKGROUND OF THE INVENTION
Hydrogen is a "clean fuel" because it can be reacted with oxygen in
hydrogen-consuming devices, such as a fuel cell or combustion
engine, to produce energy and water. Virtually no other reaction
byproducts are produced in the exhaust. As a result, the use of
hydrogen as a fuel effectively solves many environmental problems
associated with the use of petroleum based fuels. Safe and
efficient storage of hydrogen gas is, therefore, essential for many
applications that can use hydrogen. In particular, minimizing
volume, weight and complexity of the hydrogen storage systems are
important factors in mobile applications.
The development of fuel cells as replacements for batteries in
portable electronic devices, including many popular consumer
electronics such as personal data assistants, cellular phones and
laptop computers is dependent on finding a convenient and safe
hydrogen source. The technology to create small-scale systems for
hydrogen supply, storage and delivery has not yet matched the
advancements in miniaturization achieved with fuel cells.
A hydrogen fuel cell for small applications needs to be compact and
lightweight, have a high gravimetric hydrogen storage density, and
be operable in any orientation. Additionally, it should be easy to
match the control of the system's hydrogen flow rate and pressure
to the operating demands of the fuel cell.
The existing hydrogen storage options, which include compressed and
liquid hydrogen, hydrided metal alloys, and carbon nanotubes, have
characteristics which complicate their use in small consumer
applications. For instance, compressed hydrogen and liquid hydrogen
require heavy tanks and regulators for storage and delivery, metal
hydrides require added heat to release their stored hydrogen, and
carbon nanotubes must be kept pressurized.
Alternatives for hydrogen storage and generation include the class
of compounds known as chemical hydrides, such as the alkali metal
hydrides, the alkali metal aluminum hydrides and the alkali metal
borohydrides. The hydrolysis reactions of many complex metal
hydrides, including sodium borohydride, (NaBH.sub.4) have been
commonly used for the generation of hydrogen gas.
In those applications where a steady and constant supply of
hydrogen is required, it is possible to construct hydrogen
generation apparatus that control the contact of a catalyst with
the hydride fuel. Such generators typically use a two-tank system,
one for fuel and the other for discharged product. The hydrogen
generation reaction occurs in a third chamber that contains a metal
catalyst and connects the two tanks. However, such two-tank designs
are not typically directionally independent or amenable to
miniaturization.
An object of the present invention is to provide a portable
hydrogen generator that incorporates a volume-exchange tank for the
storage of the fuel solution and the discharged product and
includes a hydrogen filtration system. This device is orientation
independent and compact. Further, such a generator can utilize a
throttle valve that will enable the generator to self-regulate fuel
flow and hydrogen production.
SUMMARY OF THE INVENTION
In U.S. patent application Ser. No. 09/902,900 entitled
"Differential Pressure Driven Borohydride Based Generator, filed
Jul. 11, 2001, and owned by the present assignee, the content of
which is hereby incorporated herein by reference into the present
application in its entirety, a single volume exchanging tank is
incorporated into a hydrogen generator as part of a fuel reservoir
to feed the active fuel chamber. As fuel is consumed from the fuel
area and borate solution is returned to the borate solution area,
the movable partition slides such that space that was originally
occupied by fuel becomes occupied by borate solution. This has the
obvious advantage of reducing the overall volume needed to store
both fuel and borate solution. As the hydrolysis reaction of
chemical hydride is exothermic, the borate solution is usually
discharged at a higher temperature than the fuel solution; the
movable partition can be designed as a heat insulator to prevent
heat exchange between the two regions. This design does not,
however, provide for orientation independent operation.
The metal hydride fuel component of the disclosed system is a
complex metal hydride that is water soluble and stable in aqueous
solution. Examples of suitable metal hydrides are those having the
general formula MBH.sub.4 where M is an alkali or alkaline earth
metal selected from Group I or Group 2 of the periodic table, such
as lithium, sodium, potassium, calcium and magnesium. Examples of
such compounds include, without limitation, NaBH.sub.4, LiBH.sub.4,
KBH.sub.4, Ca(BH.sub.4).sub.2 and Mg(BH.sub.4).sub.2. These metal
hydrides may be utilized in mixtures, but are preferable utilized
individually. Preferred for such systems in accordance with the
present invention is sodium borohydride (NaBH.sub.4). Sodium
borohydride can be dissolved in alkaline water solutions with
virtually no reaction and the aqueous SBH fuel solutions are
nonvolatile and will not burn. This imparts handling and transport
ease both in the bulk sense and within the hydrogen generator
itself.
A borohydride compound will react with water to produce hydrogen
gas and a borate in accordance with the following chemical
reaction:
##STR00001## where MBH.sub.4 and MBO.sub.2, respectively, represent
a metal borohydride and a metal metaborate. The rate of
decomposition of the metal borohydride into hydrogen gas and a
metal metaborate is pH dependent, with higher pH values hindering
the hydrolysis. Accordingly, a stabilizer (such as sodium hydroxide
(NaOH)) is typically added to solutions of a complex metal hydride
(such as sodium borohydride) in water to be used as the fuel from
which the hydrogen gas is generated.
As the hydrolysis of sodium borohydride is typically slow at room
temperature, heat or a catalyst, e.g. acids or a variety of
transition metals, can be used to accelerate the hydrolysis
reaction. Transition metals from the nickel, cobalt and iron
families generally show the highest activity, and the metals or the
corresponding metal salts or metal borides can be used in solution
or as suspensions, or such salts, borides or metals can be
supported on inert substrates. In the embodiments present here, a
solid catalyst, either as a solid metal or metal boride or as
deposited on a substrate, is contained within the catalyst
chamber.
A process for generating hydrogen from such a stabilized metal
hydride solution is described in U.S. patent application Ser. No.
09/979,362, file Jan. 7, 2000 entitled "A System For Hydrogen
Generation" and the content of that application is hereby
incorporated herein by reference in its entirety.
Resulting products of the hydrogen generation process can include
hydrogen gas, borate and water among other things. It can be
appreciated that the specific dimensions as well as operating
temperatures and pressures of the system can be modified and
adapted according to the intended use of the system and according
to the specific metal hydride solution to be used without departing
from the intended purpose of the invention.
Thus the present invention includes a hydrogen gas generation
system with a housing having a hydrogen separation chamber and fuel
storage chamber and where either or both of those chambers may
include a gas permeable member to pass hydrogen through the
membrane. As another feature of the present invention, there is a
volume exchanging container having a fuel storage chamber and a
hydrogen separation chamber and either or both of those chambers
may have a gas permeable membrane located therein. As still another
feature, there may be a fuel container for containing the fuel
material and which may have a gas permeable membrane located
therein to separate any hydrogen gas from this material.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of an arrangement for a hydrogen
gas generation system in accordance with the invention;
FIG. 2 is a schematic illustration of an alternative embodiment of
a hydrogen gas generation system; and
FIG. 3 is a schematic illustration of a still further embodiment of
a hydrogen gas generation system in accordance with the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In an embodiment of the invention shown in FIG. 1, the hydrogen gas
generation system includes a housing 10 which can be constructed of
a relatively strong material as is necessary to carry out the
purposes of the present invention. Within the housing 10 there is
formed a fuel storage chamber 12 and a hydrogen separation chamber
14 separated by a flexible partition 16. The fuel storage chamber
12 normally contains the fuel solution that is reactive to produce
hydrogen gas and is a hydride solution and can be a stabilized
metal hydride solution, such as sodium borohydride.
The flexible partition 16 can be a ribbon spring or a preformed
piece of flexible plastic or similar material that has an intrinsic
tension and can maintain an applied pressure on the fuel solution
within the fuel storage chamber 12. When the fuel storage chamber
12 is full of the fuel solution, the flexible partition 16 is
expanded into a high energy "extended" state. As the flexible
partition 16 contracts as the fuel solution is depleted, the
flexible partition 16 returns to its lowest energy "original"
state, it compresses the fuel solution and forces that fuel
solution out of the fuel storage chamber and into the fuel conduit
18.
The fuel conduit 18 conducts the fuel solution from the fuel
storage chamber 12 to an inlet 20 in the catalyst chamber 22 which
contains the catalyst to enhance the reaction of the fuel solution
to produce hydrogen gas. The catalyst used with this embodiment can
comprise various catalysts known to be useful for the present
application and can be ruthenium metal deposited on a metal mesh
prepared as described in PCT Publication No. WO 01/51410 and
entitled "System For Hydrogen Generation".
The reaction results in the generation of hydrogen gas along with
the formation of other materials such as borate and water and which
shall simply be referred to as discharged fuel. That discharged
fuel along with hydrogen thereby produced leaves the catalyst
chamber 22 via an outlet 24 and passes through an outlet conduit 26
where the discharged fuel and hydrogen enters the hydrogen
separation chamber 14. Within the hydrogen separation chamber 14,
the hydrogen gas separates from the discharged fuel and passes
upwardly to exit from the hydrogen separation chamber 14 through
the hydrogen gas outlet 28 where the hydrogen is collected and
channeled to an end use device to derive the energy from the
hydrogen gas.
A fuel shut off valve 30 may be present in the fuel conduit 18 to
act to shut off and/or control the flow of fuel solution passing
from the fuel storage chamber 12 to the catalyst chamber 22 and
impart manual or automated control over the production of hydrogen
gas.
There is also a first gas permeable membrane 32 located in the fuel
storage chamber 12 in the upper area thereof and which allows
hydrogen gas to pass through the gas permeable membrane 32 while
preventing the fuel solution from passing therethrough. Examples of
suitable gas permeable membranes include those materials known to
be more permeable to hydrogen than water such as silicon rubber,
fluoropolymers or any of the common hydrogen-permeable metal
membranes such as palladium-gold alloys.
Accordingly, any hydrogen gas that is produced spontaneously in the
fuel solution while it is present and at rest in the fuel storage
chamber 12 due to the reaction of the fuel solution, and that
hydrogen gas passes through the gas permeable membrane 32 and
enters the space 34 where that hydrogen gas can be drawn off via a
discharge conduit 36 and/or the hydrogen gas can be allowed to pass
through pores or other openings in or around the flexible partition
16 to enter the hydrogen separation chamber 14 and continue to
progress upwardly to join and exit the hydrogen separation chamber
14 along with the hydrogen gas normally produced by the reaction of
the fuel solution by the reaction that takes place within the
catalyst chamber 22 and which enters the hydrogen separation
chamber 14 by means of the outlet conduit 26.
A second gas permeable membrane 33 is also preferably located in
the hydrogen separation chamber 14 to allow the hydrogen in that
chamber to pass through the second gas permeable membrane 33 and
outwardly through the hydrogen gas outlet 28 while preventing any
of the discharged fuel from passing therethrough such that the
discharged fuel is contained within the hydrogen separation chamber
14 so that the hydrogen gas can be recovered through the hydrogen
gas outlet 28 for use with the end utilization device.
The gaseous hydrogen is separated from the discharged fuel by means
of gravity in the hydrogen separation chamber 14 and the gaseous
hydrogen leaves the hydrogen separation chamber 14 through the
second gas permeable membrane 33 and the hydrogen gas outlet 28 for
use in supplying energy to an end utilization device, such as a
fuel cell in a laptop computer or a cell phone.
As such, in the operation of the hydrogen gas generating system,
the flexible partition 16 exerts a force within the fuel storage
chamber 12 to initialize the reaction by forcing the fuel solution
through the catalyst chamber 22 to produce the hydrogen gas and the
discharged fuel. The discharged fuel enters the hydrogen separation
chamber 14 and the discharged fuel adds weight to the flexible
partition 16 to continue to force the fuel solution outwardly from
the fuel storage chamber 12 through the catalyst chamber 22 as the
production of hydrogen gas continues.
In another embodiment of the invention shown in the schematic
illustration of FIG. 2, the housing 10 also has formed therein a
fuel storage chamber 12 and a hydrogen separation chamber 14. In
the FIG. 2 embodiment there is a movable partition 38 that is
located intermediate the fuel storage chamber 12 and the hydrogen
separation chamber 14 and which is movably positioned within the
housing 10. Within the fuel storage chamber 12, there is first
flexible bag 40 comprised of a plastic material, such as nylon, and
which contains the fuel solution that is discharged via an outlet
42 in the first flexible bag 40 so that the fuel solution can enter
the fuel conduit 18 and the catalyst chamber 22 where the reaction
takes place and the discharged fuel along with hydrogen gas passes
through the outlet conduit 26 where it enters a inlet 44 in a
second flexible bag 46. The second flexible bag 46 is also
preferably made of a plastic material, such as nylon.
In the walls of each of the first and second flexible bags 40, 46,
there is located first and second gas permeable membrane windows
48, 50, respectively, so that hydrogen can readily pass through the
walls of the first and second bags 40, 46 in a manner and for a
purpose to be described.
As a further feature of the FIG. 2 embodiment, the movable
partition 38 is biased toward the first flexible bag 40 in order to
create and maintain a pressure within the first flexible bag 40 to
push the fuel solution within the first flexible bag 40 outwardly
through the fuel conduit 18 and thus through the catalyst chamber
22 in the operation of the gas generating system. As shown in FIG.
2, that bias may be created by a spring 52 that is located between
the housing 10 and the movable partition 38 so that the spring 52
can create the bias on the movable partition 38. Obviously, other
means can be used to create a bias on the movable partition 38 to
urge it in the direction of the first flexible bag 40 to expel the
fuel solution out of the first flexible bag 40 to operate the gas
generating system of the present invention.
Returning now to the first and second gas permeable membrane
windows 48, 50, the first gas permeable membrane window 48 is
formed in the wall of the first flexible bag that contains the fuel
solution and, as explained, there is formed a quantity of outgassed
hydrogen spontaneously caused by the presence of the fuel solution
within the first flexible envelope 40 and therefore, that out gas
hydrogen can pass through the first gas permeable membrane window
48 to pass out of the first flexible bag 40 to enter the space 34
bounded by the interior of housing 10 and the exterior of first
flexible bag 40 and second flexible bag 46. That outgassed hydrogen
can then be allowed to pass through openings in or around the
movable partition 38 to pass outwardly through the hydrogen outlet
28, or, alternatively, be removed by means of a separate discharge
conduit 36 for use to provide power to the particular end use
device.
In a similar manner, the second gas permeable membrane window 50
formed in the wall of the second flexible bag 46 allows the
hydrogen generated by the reaction that takes place in the catalyst
chamber 22 to pass through the wall of the second flexible bag 46
so that such hydrogen gas can pass through the hydrogen gas outlet
28 and, again, to exit the housing 10 for use in powering some end
use device.
In the operation of the FIG. 2 embodiment, therefore, the bias of
the spring 52 causes the movable partition 38 to push against the
first flexible bag 40 to expel the fuel solution out of the first
flexible bag 40 and into the fuel conduit 18 to pass through the
catalyst chamber 22 to enhance the reaction of the fuel solution to
generate hydrogen gas that ultimately passes out of the housing 10
through the hydrogen gas outlet 28. As shown in FIG. 2, the bias is
exerted by the spring 52, however, the movable partition 38 could
be driven by any device that applies a force to compress the fuel
such as a spring-loaded plate, gas-charged pistons or wafer
springs. As the second flexible bag 46 fills with the discharged
fuel, it can exert additional pressure on the movable partition 38
in some orientations to further forcing additional fuel into the
catalyst chamber 22.
As an example, the hydrogen gas generating system of FIG. 2 was
constructed from a plastic gastight box fitted with a hydrogen gas
outlet valve and tested experimentally. The hydrogen gas outlet 28
was connected to a 50 watt fuel cell with a 24 watt load. To begin
testing, an empty bag, the second flexible bag 46, constructed of
layers of nylon and polypropylene with a fluoropolymer membrane was
placed in the hydrogen separation chamber 14 and connected to a
bulkhead fitting that extended through the wall of the housing 10
to connect the second flexible bag 46 to the outlet conduit 26 from
the catalyst chamber 22.
Another bag, the first flexible bag 40, was filled with an aqueous
solution of sodium borohydride and placed in the housing 10 and
occupied the majority of the fuel storage chamber 12 and compressed
the spring loaded movable partition 38. That compression created a
constant pressure on the first flexible bag 40 forcing the fuel to
flow through the outlet 42. The first flexible bag 40 was connected
by a series of valves, including a check valve, a ball valve, a
solenoid valve and a needle valve to the inlet 20 of the catalyst
chamber 22 which was located outside the housing 10. The spring
loaded movable partition 38 maintained a positive pressure on the
first flexible bag 40.
The fuel shut-off valve 30 was opened to allow the fuel to flow
from the first flexible bag 40 through the catalyst chamber 22 to
produce hydrogen and mixture of sodium borate in water. This valve
30 can be manually powered or powered by a DC power module. The
borate and hydrogen were discharged from the catalyst chamber 22
into the empty second flexible bag 46. The hydrogen gas, but none
of the borate or liquid water, passed through the second gas
permeable membrane window 50 into the interior of the housing 10,
while retaining the borate and water in the second flexible bag 46.
The second gas permeable membrane window 50 prevented the large
solid particles from reaching the fuel cell as such particles were
retained within the second flexible bag 46.
A pressure switch was used to regulate the pressure of hydrogen
within the housing 10 to prevent over-pressurization. When the
pressure reached a pre-set limit, a solenoid valve was operated to
shut off the flow of fuel to the catalyst chamber 22 and halt the
production of hydrogen. When hydrogen was removed from the housing
10, the solenoid valve was operated to resume the flow of fuel and
hydrogen production. The hydrogen gas generator maintained a
hydrogen pressure between about 2 and 5 psi. and acceptable load
following was observed.
Turning now to FIG. 3, there is a schematic illustration of a
further embodiment of the present invention and where there is a
throttle valve 54 interposed in the fuel conduit 18 to control the
reaction carried out in the catalyst chamber 22.
As with the FIG. 2 embodiment, therefore, the housing 10 encloses a
fuel storage chamber 12 and a hydrogen separation chamber 14
separated by a movable partition 38. Again the movable partition
38, by means of the spring 52, is pressurized so as to propel the
fuel solution through the fuel conduit 18 and thereafter through
the catalyst chamber 22 where hydrogen gas is produced and the
hydrogen gas along with the discharged fuel passes through the
outlet conduit 26 to the interior of the second flexible bag 46
where the hydrogen gas is separated by gravity to pass through the
hydrogen gas outlet 28 and into a control pressure conduit 56.
In the FIG. 3 embodiment, however, the throttle valve 54 is used to
control the reaction that takes place in the catalyst chamber 22 by
controlling the flow of fuel solution from the first flexible bag
40 to the catalyst chamber 22 and comprises a valve body 56 having
a passageway 58 therethrough. The fuel passes through the
passageway 58 as it progresses through the fuel conduit 18 and,
therefore, by controlling the cross sectional area of the
passageway 58 it is possible to control the flow of the fuel
solution that reaches the catalyst chamber 22 and thus, also
control the reaction that takes place in the catalyst chamber
22
Accordingly, there is a valve operator 60 having a tapered leading
edge 62 that enters the passageway 58 such that the movement of the
valve operator 60 with respect to the passageway 58 can control the
flow of the fuel solution passing through the passageway 58 by
creating a variable orifice. The movement of the valve operator 60
is, in turn controlled by a diaphragm 64 and a pressure chamber 66
such that a change in pressure causes movement of the valve
operator 60. A spring 67 can also be employed to increase the
sensitivity of the throttle valve 54.
The pressure in the pressure chamber 66 is established by the
hydrogen that passes outwardly from the hydrogen gas outlet 28
through a hydrogen conduit 68. As can be seen in FIG. 3, the
hydrogen conduit 68 communicates with the pressure chamber 66 and
there is a back pressure control valve 70 located on the downstream
side of the pressure chamber 66.
The operation of the throttle valve 54 can now be described for
controlling the reaction that takes place in the catalyst chamber
22. Once the reaction has been commenced by the fuel solution being
forced through the catalyst chamber 22 by the pressure within the
first flexible bag 40, hydrogen gas is produced that passes out of
the hydrogen gas outlet 28 and through the hydrogen conduit 68 to
ultimately pass out of a downstream hydrogen outlet 72.
As the hydrogen gas passes through the pressure chamber 66, there
is a pressure established, controlled by the back pressure control
valve 70, such that the pressure in the pressure chamber 66, and
thus the position of the valve operator 60 is controlled by the
hydrogen passing through the hydrogen conduit 68. The reaction that
takes place in the catalyst chamber 22 is therefore
self-regulating, that is, as the reaction increases, additional
hydrogen is produced and increases the flow of hydrogen in the
hydrogen conduit 68, thereby raising the pressure within the
pressure chamber 66 to force the leading edge 62 of the valve
operator 60 further into obstructing the passageway 58, or
narrowing the orifice, carrying the fuel solution such that the
reduction in that flow of fuel solution slows the reaction that
takes place in the catalyst chamber 22. As a result, the amount of
hydrogen produced is reduced. The same regulation takes place as
the reaction slows in the catalyst chamber 22 and the production of
hydrogen is reduced, that is, the effective area of the passageway
58 is then increased, thereby increasing the flow of the fuel
solution and increasing the reaction within the catalyst chamber
22.
As such, the reaction within the catalyst chamber 22 is regulated
by the use of the throttle valve 54 and the reaction further
established by regulating the flow of the product hydrogen
converted to pressure by the back pressure valve 70.
The foregoing description has been presented to enable those
skilled in the art to more clearly understand and practice the
instant invention. It should not be considered as limitations upon
the scope of the invention, but as merely being illustrative and
representative of several embodiments of the invention. Numerous
modifications and alternative embodiments of the invention will be
apparent to those skilled in the art in view of the foregoing
description. For example, while the membranes 32, 33, 48 and 50
have been described as being gas permeable so as to isolate the
hydrogen gas from the fuel material or discharged fuel. Many
membrane materials that are permeable to hydrogen gas are also
hydrophobic. In certain applications, it is preferable for the
membrane to be hydrophobic in addition to being gas permeable.
* * * * *